Studies in Cell Suspension Cultures of Cassia didymobotrya. Part II. The Biotransformation of Chalcones to Flavonones

An enzyme system derived from cell cultures of Cassia didymobotrya Showed, inter alia, a chalcone - flavanone isomerase which revealed a maximum activity when isolated from 22 day old cultures. Its substrate specificity was demonstrated by using sixteen chalcones featuring different substitutions patterns in rings A and B. The highest yields of flavanone formation were observed with various ring A functionalyzed chalcones lacking functionality in ring B. The chalcones having an isoprenyl side chain in the 3'- position of ring A were not transformed. The presence of a free hydroxyl group at C-4 of ring B stimulated flavanone formation relative to other ring B substrates. Some comments concerning the possible mechanism of the chalcone - flavanone isomerase reaction are provided.